north-western coast of Scotland and in the islands connected with it. The interval between these two principal masses of sandstone may be said, in a general way, to extend from near the Mull of Cantyre to Kintail, and the predominant rocks throughout this space are gneiss, micaceous schist, quartz rock, and a variety of analogous substances which it would be out of place to enumerate here.
It is in this interval that the scattered fragments of the sandstone strata are to be occasionally found, sometimes like that near the foot of Cruachan, connected only with the more ancient rocks, in other places associated with and covered by a variety of rocks more or less appertaining to the trap family, or to the porphyritic rocks which accompany them. It would lead to a length of description unfit for this paper to describe the places where they are to be seen, but I may mention two which are remarkable on account of the narrow space which the sandstone occupies, still more limited than even in the spot which has led to this discussion. These are the island of Seil, and Inish capel, in the latter of which their total extent only amounts to a very few yards. It is remarkable that in all these cases, as far at least as I have examined them, their dip is toward the west, however limited this may be, and that this is also the dip of the leading masses both at the southern side of the interruption above quoted and at its northern extremity where the same strata are found occupying parts of many of the islands, and extending for a considerable space between Kintail and the Ru Storr in Assynt.
The uniformity of their dip proves that these independent masses have not been separated by any disturbance from below, and we have therefore to chuse only between two explanations; either that they had been originally independent deposits, or that they had formed one mass subsequently disjoined either by the operations of water or of other destroying forces acting on the surface, or else
